When firing infantry weapons, such as rifles, assault rifles, grenade launchers and mortars, aiming of the weapon barrels is performed manually in most cases by aiming at the target without the aid of a fire control device.
Prior to firing it is necessary to set a gun sight angle at the weapon, which is a function of the deployment distance by which the target is distant from the weapon. In connection with direct firing, that angle by which the weapon must be aimed higher than the aiming line is called the gun sight angle. In direct firing the projectiles fired from the weapon barrel move on a projectile trajectory which coincides with the aiming line at the mouth of the weapon barrel, then lies above the aiming line and then should again coincide with the aiming line at the target. Therefore the exact setting of the gun sight angle is imperative for making hits, and the deployment distance must be exactly known for determining the gun sight angle.
In connection with direct firing, for which light infantry weapons are primarily employed, aiming for the target is made by the naked eye. The deployment distance, i.e. the distance to the target, is determined without any aids. However, it is almost impossible to exactly determine the deployment distance by the naked eye, therefore a distance range, within which the exact deployment distance is presumed to lie, is generally estimated. In certain cases, namely if the topographic position of the target is known, the deployment distance can be exactly determined by means external to the weapon, for example with the aid of a topographic map. It is also possible to measure the deployment distance to a visible target with the aid of a distance measuring unit, for example a laser distance measuring unit.
Medium and heavy infantry weapons in particular are also used for indirect firing, i.e. for hitting targets which are separated from the weapon by an impermeable obstacle and are not visible. In this case the deployment distance cannot be measured. It must either be estimated without a visual aid on the basis of a possible, or presumed position of the target, or it must be determined with the aid of means external to the weapon.
In direct firing, aiming for the target can take place by the naked eye with the aid of a simple aiming device, for example a conventional rear/front sight aiming device, without any optical device.
But rear/front sight aiming devices have two large disadvantages, which result in the inability to precisely aim the weapon barrel: for one, the deployment distance is only approximately known in most cases, since it must be estimated by the naked eye; furthermore, there is only a vague image of the target because of the lack of an optical enlargement, and the weapon can therefore not be stably aimed.
Infantry weapons can also have optical aiming devices as aids in aiming for the target. Such aids which, within the scope of the present specification will be generally called image visualization units, can have telescopic sights, for example. In this case the rifleman can see an enlarged image of the target, or a target image, as well as markings engraved in the image visualization unit, or a target mark. The determination of the deployment distance takes place either as described above by the naked eye, or with the aid of a laser distance measuring unit. The telescopic sight is mounted in such a way that its optical axis is aimed parallel with the weapon barrel axis, and the possibly also provided laser distance measuring unit is aimed parallel with the weapon barrel axis. If no gun sight angle were to be taken into consideration, this would lead to corresponding inaccuracies. This problem becomes more serious in connection with slow-flying projectiles, such as grenades, since the long flying time of such projectiles demands a comparatively large gun sight angle.
Essentially, the disadvantages of the image visualization unit in the form of a telescopic sight are the following: The orientation of the telescopic sight parallel with the weapon barrel limits the selection of the enlargement; a gun sight angle, which must be set at the weapon, determines the deviation between the aiming line and the weapon barrel axis, by means of which a target marker is displayed; if the deployment distance is too great, these gun sight angles are relatively large, which has the result that the target marker can no longer be displayed in an optical device capable of considerable enlargement. Moreover, distortions are received in case of too large a deviation, unless an optical device is employed which is absolutely free of distortion and therefore expensive.
In summary it can be stated that up to now no devices which permit exact sighting of the target and aiming of the weapon barrel are known for infantry weapons. This was not considered to be a great lack, as long as the projectiles fired from infantry weapons were equipped with contact fuses to a large extent. But it is preferred to also fire projectiles with programmable ignition, which detonate prior to impact, from infantry weapons; such projectiles are also called ABM [Air Burst Munitions]. ABM have numerous advantages over conventional munitions: the ABM projectiles penetrate concealing bushes or thin woods, as well as masses of snow of considerable thickness, without detonating prematurely; ABM are excellently suited for house-to-house fighting, since window panes and thin walls are penetrated and the effect of the projectile is directed forward; the feared ricochet effect, which otherwise often occurs with conventional munitions and extended projectile trajectories, cannot occur. However, the use of ABM can only be successful if it is possible to accurately determine the projectile trajectories, or when the weapons used have devices which permit the exact sighting of the target and aiming of the weapon barrel.
Weapons systems with fire control devices which permit swift aiming, some even on rapidly moving targets, are known in the fields of artillery and anti-aircraft artillery. However, the technology of these very elaborate weapons systems cannot be transferred to infantry weapons, which should be simple in construction and handling, cost-effective, light and mobile to the highest degree, and must operate autonomously.